Surplus-bone disorders illustrate the need that our bodies have to keep BMPs under control. Yet fused fingers and even thick skulls are relatively mild manifestations of the ability of BMPs to produce bone in inconvenient places. Another disease shows the extent of what can go wrong when osteoblasts proliferate throughout the body and make bone wherever they please. The disorder is known as fibrodysplasia ossificans progressiva or FOP. It is rare: estimates put the number of people afflicted with it worldwide at about 2500, but only a few hundred are actually known to specialists in the disease. Its most famous victim was an American man by the name of Harry Raymond Eastlack. In 1935, Harry, then a five-year-old, broke his leg while playing with his sister. The fracture set badly and left him with a bowed left femur. Shortly afterwards, he also developed a stiff hip and knee. The stiffness was not, however, caused by the original break, but rather by bony deposits that had grown on his adductor and quadriceps muscles.
FIBRODYSPLASIA OSSIFICANS PROGRESSIVA. HARRY EASTLACK, USA 1953.
As Harry grew older, the bony deposits spread throughout his body. They appeared in his buttocks, chest and neck and also his back. By 1946 his left leg and hip had completely seized up; his torso had become permanently bent at a thirty-degree angle; bony bridges had formed between his vertebrae, and the muscles of his back had turned to sheets of bone. Attempts were made to surgically excise the bone, but it grew back – harder and more pervasive than before. At the age of twenty-three, he was placed in an institution for the chronically disabled. By the time of his death in 1973, his jaws had seized up and he could no longer speak.
Harry Eastlack requested that his skeleton be kept for scientific study, and today it stands in Philadelphia’s Mutter Museum. Bound in extra sheets, struts and pinnacles of bone that ramify across the limbs and ribcage, the skeleton is, in effect, that of a forty-year-old man encased in another skeleton, but one that is inchoate and out of control. The cause of the disease is understood in general terms. The bodies of FOP patients do not respond to tissue trauma in the normal way. Bruises and sprains, instead of being repaired with the appropriate tissue, are repaired with osteoblasts and the new tissue turns to bone. This has all the hallmarks of an error in BMP production or control, but the mutation itself has not yet been identified. The search may well be a long one. FOP patients rarely have children, so the causal gene cannot be mapped by searching through long pedigrees of afflicted families.
FIBRODYSPLASIA OSSIFICANS PROGRESSIVA. HARRY EASTLACK (1930–73).
GROWING BONES
A newly born infant has a skeleton of filigree fineness and intricacy, a skull as soft as a sheet of cardboard but scarcely as thick, and femurs as thin as pencils. By the time the child is an adult all this will have changed. The femur will have the diameter of a hockey stick, and will be able to resist the impact of one as well, at least most of the time. The skull will be as thick as a soup plate and capable of protecting the brain even when its owner is engaged in a game of rugby or the scarcely less curious customs of the Australian Aborigines who ritually beat each other’s skulls with thick branches.
What makes bones grow to the size that they do? In 1930 a young American scientist, Victor Chandler Twitty, tackled this question in a very direct way. Taking a cue from the German Entwicklungsmechanik, Twitty chose to study two species of salamanders: tiger salamanders and spotted salamanders. Closely related, they differ in one notable respect: tiger salamanders are about twice as big as spotteds. The experiment he carried out on them was of such elegance, simplicity and daring that seventy years later it can still be found in textbooks.
Twitty began by cutting the legs off his salamanders. The Italian scientist Lazzaro Spallanzani of Scandiano had discovered in 1768 that salamanders can regrow, should they need to, their legs and tails. Since then, thousands of the creatures have lost their legs to science. One luckless animal had a leg amputated twenty times – and grew it back each time. It is sometimes facetiously remarked among scientists that happiness is finding an experiment that works and doing it over and over again. Twitty, however, was more ingenious. As the stumps of his salamanders healed, and as their tissues reorganised into limb-buds, he once again put them to the knife. He then took the severed limb-buds of each species and grafted them onto the stumps of the other.
The question was, how big would the foreign limbs grow? There were, Twitty reasoned, two possibilities. As the grafted buds grew into legs, they might take on the properties of their host, or they might retain their own. If the first, then a spotted salamander limb-bud grafted onto a tiger salamander should grow into a hefty, tiger salamander-sized leg. Alternatively, the spotted salamander limb-bud might simply grow into the small leg that it usually does. The result would be tiger salamanders with three large legs and one tiny grafted one, and spotted salamanders with three tiny legs and one large grafted one – in short, lopsided salamanders.
Twitty expected that the foreign legs would grow as large as the host salamanders’ normal legs. By the 1930s it was known that hormones have an immense influence over human growth. One, produced by the pituitary gland, had even been dubbed ‘growth hormone’, and clinicians spoke of people with an excess or deficiency of this hormone as ‘pituitary’ giants and dwarfs. If tiger salamanders were larger than spotted salamanders, it was surely because they had more growth hormone (or something like it) than their smaller relatives. Foreign limbs should respond to the hormone levels of their hosts no less than ordinary limbs and should become accordingly large or small. The control of growth would be, in a sense, global – a matter of tissues being dictated to by a single set of instructions that circulate throughout the whole body.
There is no doubt that hormones do play a role – a vital role – in how large salamanders, people, and probably all animals become. But the beauty of Twitty’s experiment is that it showed that, however important hormones are, they are not responsible for the difference between large and small salamanders. Against expectation, his salamanders proved lopsided. It seemed as if the grafted limbs, in some ineffably mysterious way, simply knew what size they should be regardless of what they were attached to. It was an experiment that showed the primacy of the local over the global, and that each salamander leg contains within itself the makings of its own fate.
The reward of these experiments was, for Twitty, enduring fame of a modest sort. More immediately, in 1931 he got to go to Berlin. He went to work at the laboratory of Otto Mangold, husband of Hilda Pröscholdt of organiser fame, at the Kaiser Wilhelm Institute. There he met some of the great biologists of the day: Hans Spemann, Richard Goldschmidt and Viktor Hamburger, who together had made Germany pre-eminent in developmental biology. Neither Twitty’s research at the Kaiser Wilhelm, nor his later career as a much-loved Stanford professor, are of particular interest to us, but the time and the country are. Four hundred kilometres to the south, in Munich, another young scientist with similar research interests, but of a rather different stamp, had just started medical school. This was Josef Mengele.
AUSCHWITZ, 1944
The man whose name forever casts a shadow over the study of human genetics came from a well-to-do family of Bavarian industrialists. Handsome, smooth and intelligent, he refused to join the family firm and instead studied medicine and philosophy at Munich University. He was ambitious, and desired ardently to make a name for himself as a scientist, the first of his family. By the mid-1930s he had moved to Frankfurt where he became the protégé of Otamar Freiherr von Verschuer, head of another Kaiser Wilhelm Institute, but one devoted to anthropology. The dissertation that Mengele wrote there in 1935 reflects the prevailing obsession of German anthropology with racial classification and involved the measurement of hundreds of jawbones in a search for racial differences. Two later papers are about the inheritance of certain disorders such as cleft palate. All these works are dry, factual, and rather dull. They contain no hint of the young scientist’s future career.
Mengele arrived at Auschwitz on 30 May 1943. He had
been urged to go there by his mentor, von Verschuer, and it was von Verschuer too who had urged Mengele to take advantage of the, as it was put to him, ‘extraordinary research opportunities’ he would find there. By the time he arrived at the concentration camp, it contained just over a hundred thousand prisoners and the killing-machine was fully engaged.
Mengele was only one of many medical staff at Auschwitz-Birkenau, and he was not particularly senior. But after the war, it would be Mengele whom the survivors would remember. They would remember him for his physical beauty, the exquisiteness of his uniform, his charm, and his smile. They would remember him for the unfathomable quality of his personality: he was a man who could speak kindly to a child and then send it to a gas chamber. They would remember him because he was ubiquitous, and also because he was often the first German officer they saw. As the prisoners stepped from the cattle-cars onto the platform at Birkenau, they would hear him shout ‘Links‘ or ‘Rechts‘. ‘Left’ and they would die immediately, ‘Right’ and they were spared, at least for a time.
Among those spared was a thirty-year-old Jewish woman named Elizabeth Ovitz. She and her siblings arrived at Auschwitz-Birkenau on the night of 18 May 1944. They were brought there in a cattle-car containing eighty-four other people. Weak and disoriented from the journey, the Ovitzes stood on the Birkenau railway platform under the glare of arc lights. Elizabeth asked a prisoner, a Jewish engineer from Vienna, where they were. He replied, ‘This is the grave of Israel,’ and pointed to the smokestacks that towered over the camp. Forty-three years later she would write: ‘Now we realised everything that we knew before, and had tried to erase from our consciousness, would actually come about.’ Elizabeth and her siblings, twelve in all, were herded to one side. It was then that they met Mengele. Surveying them with fascination he declared: ‘Now I will have work for the next twenty years; now science will have an interesting subject to consider.’
The Ovitzes were Transylvanian Jews. Their father, Shimshon Isaac Ovitz, had been a scholar and Wonder-rabbi. He had a form of dwarfism called pseudoachondroplasia that leaves much of the body unaffected but causes the limbs to grow short and bowed. Rabbi Ovitz was renowned for his wisdom and compassion. Many Romanian Jews believed that, having been denied normal height by God, he was instead endowed with extraordinary and rare virtues. Amulets containing bits of parchment decorated in his finely curling Rashi script were said to have healing powers. Rabbi Ovitz had nine children of whom seven, including Elizabeth, were dwarfed. This is consistent with a diagnosis of pseudoachondroplasia, which is caused by a dominantly inherited mutation.
When Elizabeth was nine years old, her father died suddenly. His young widow, a resourceful woman, reasoned that the short stature of her children could be used to their advantage and gave them a musical education so that they could eventually form a troupe. Even as Romania and Hungary were drawn within the orbit of Nazi Germany, the Ovitz family took their ‘Jazz Band of Lilliput’ through the provincial towns of the fragmented and unstable states of Central Europe. In May 1942 Elizabeth Ovitz, now twenty-eight, met a young theatre manager named Yoshko Moskovitz. He was tall and handsome and besotted with her. He wrote to his sister that he had met a woman, small in size, but well endowed with talent, wisdom and industriousness. They married in November of the same year, but only ten days after the wedding Yoshko, a yellow Star of David on his coat sleeve, was drafted into a labour battalion. The couple would not see each other again until after the war. Concealing their Jewish identities, the Ovitzes continued to tour for another two years, but in March 1944 German troops occupied Hungary and, as the last and greatest of all pogroms rolled across the country, they were caught.
At Auschwitz, Elizabeth and her siblings were kept in a separate room so that they would not be crushed by the other five hundred inmates of the block; they were also allowed their own clothes and enough food to live on. For a while they were able to stay together as a family, and managed to persuade Mengele that they were related to another family from their village. They paid for survival by being given starring roles in Mengele’s bizarre and frenetic programme of experimental research.
As Elizabeth Ovitz would write: ‘the most frightful experiments of all [were] the gynaecological experiments. Only the married ones among us had to endure that. They tied us to the table and the systematic torture began. They injected things into our uterus, extracted blood, dug into us, pierced us and removed samples. The pain was unbearable. The doctor conducting the experiments took pity on us and asked his superiors to stop them, otherwise our lives would be in jeopardy. It is impossible to put into words the intolerable pain that we suffered, which continued for many days after the experiments had ceased.
‘I don’t know if our physical condition influenced Mengele or if the gynaecological experiments had simply been completed. In any event, the sadistic experiments were halted, and others begun. They extracted fluid from our spinal chord and rinsed out our ears with extremely hot or cold water which made us vomit. Subsequently the hair extraction began again and when we were ready to collapse, they began painful tests on the brain, nose, mouth and hand regions. All stages of the tests were fully documented with illustrations. It may be noted, ironically, that we were among the only ones in the world whose, torture was premeditated and “scientifically” documented for the sake of future generations…’
In this, however, Elizabeth was wrong. Mengele tortured many other people as well, including a large number of twins whom he ultimately killed and dissected for the sole purpose of documenting the similarity of their internal organs. The Ovitz family walked the tightrope of Mengele’s obsessions for seven months. Once, when Mengele unexpectedly entered the compound, the youngest of the family, Shimshon, who was only eighteen months old, toddled towards him. Mengele lifted the child into his arms and softly enquired why the child had approached him. ‘He thinks you are his father.’ ‘I am not his father,’ said Mengele, ‘only his uncle.’ Yet the child was emaciated from the poor food and the incessant blood sampling.
Mengele displayed the Ovitzes to senior Nazis. He lectured on the phenomenon of dwarfism and illustrated it with the family, who stood naked and shivering on the stage. The experiments continued until October 1944. Even as the Third Reich entered its death-throes, Mengele still brimmed with maniacal purpose, producing a collection of glass eyes from which he sought a match to Elizabeth’s brown ones. As with all he did, his reason for doing so remains unfathomable.
PSEUDOACHONDROPLASIA. ELIZABETH OVITZ (1914–92), FAR LEFT, AND SIBLINGS. BAT GALIM, ISRAEL c.1949.
Auschwitz was liberated on 27 January 1945. For Elizabeth and her family the arrival of Soviet troops lifted a sentence of certain death. Nearly all of Mengele’s experimental subjects were killed once he had done with them. During the following four years the family would shuttle about the wreckage of Eastern and Central Europe. Reforming their troupe, they choreographed a grim tango that they called their Totentanz. Each night Elizabeth, partnered by one of her brothers, would dance the part of Life to his Death. In 1949 the family emigrated to Israel. Elizabeth Ovitz died in Haifa in 1992. Josef Mengele was never tried for his crimes, but died on a Brazilian beach in 1979.
THE BRAKE
Of the many grim ironies that the history of the Ovitz family presents us with, perhaps the greatest is that when Josef Mengele perceived that they were remarkable, he was right. People with disorders such as pseudoachondroplasia do tell us something important about how bones grow to the lengths that they do, and how tall we become. Mengele did not discover what this is, nor could his pointless experiments ever have told him. But half a century later it is clear that the stubby, bent and warped limbs that are the consequence of so many bone disorders speak of the phenomenon that Victor Twitty discovered: the local control of growth.
Nowhere is the dynamic nature of bone more apparent than at the ends of an infant’s long bones. Each end has a region, the growth plate, from which the bone grows. Unlike the rest of the bo
ne, which is encased in calcium phosphate, the growth plates are soft and uncalcified. On a radiogram they appear as transverse shadows that bisect the white tips of each bone. They can be seen throughout childhood and adolescence, ever decreasing in size, until by age eighteen or so they become sealed over and linear growth stops.
Each growth plate contains hundreds of columns of chondrocytes dividing and differentiating in lock step. Born at the end of the growth plate furthest away from the bone-shaft, they then swell with proteins from which they spin a cartilaginous matrix around themselves and then die. Osteoblasts march over the graves of chondrocytes, deposit calcium phosphate and yet more matrix, and at both ends the bone pushes ever further out into space.
Pseudoachondroplasia – the disorder that afflicted the Ovitzes – throws this sequence of events into disarray. The mutation occurs in a gene that encodes one of the proteins that goes into the cartilaginous matrix that chondrocytes make. Instead of being secreted, hoewever, the mutant protein accumulates in the chondrocytes, poisoning and killing them long before their time. Not all of the chondrocytes die, but the toll is enough to drastically slow growth. The result is short, bent limbs, but a torso and face that are hardly affected at all.
Pseudoachondroplasia is only one of several disorders that cause very short limbs. Another is the disorder with which it was long confused – achondroplasia itself. From Ptah-Pataikoi, dwarf deity of youth, creation and regeneration in Egypt’s New Kingdom (1539–750 BC) to television advertisements for carbonated soft-drinks, there is no more common disorder in the iconography of smallness. Like its namesake, achondroplasia is caused by a shortage of chondrocytes travelling up the growth plate – but a shortage that has a very different origin.
Achondroplasia is caused by a mutation in a receptor for fibroblast growth factors. FGFs are the signalling molecules involved in the molecular clock regulating the near to the far axis of the foetal limb. After birth, however, FGFs, far from promoting the outgrowth of the limb, inhibit it.
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